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From simple linear cinnamyl ethers to complex tetrahydropyranes with high diastereocontrol via Ag(i) initiation of a cationic chain.

Trinuclear all-metal aromatic clusters are an original class of molecules with a cyclic and planar metal core. Characterized by peculiar metal-metal delocalized bonds, they represent a new frontier in transition-metal catalysis. We report a study on C-C-forming reactions of polyunsaturated substrates catalyzed by trinuclear all-metal aromatic palladium clusters. The synthesis of two new families of tricyclic compounds was obtained with a broad functional group tolerance under mild reaction conditions. A peculiar regio- and diastereoselectivity characterized the method, demonstrating that trinuclear palladium complexes are complementary to their popular mononuclear peers. Furthermore, preliminary studies on the mechanism of these polycyclization reactions revealed unique features of the homogeneous catalytic system.

Katritzky salts have emerged as effective alkyl radical sources upon metal- or photocatalysis. These are typically prepared from the corresponding triarylpyrylium ions, in turn an important class of photocatalysts for small molecules synthesis and photopolymerization. Here, a flow method for the rapid synthesis of both pyrylium and Katrizky salts in a telescoped fashion is reported. Moreover, several pyrylium salts were tested in the photoinduced RAFT polymerization of vinyl ethers under flow and batch conditions.

A chemoselective method for the carbonylation of allylic substrates CH2=CHCH2X (X= OAc, OC(O)CH2CN, OPh, OEt, OC(O)OPh, OC(O)OiBu, N(H)C(O)Ph, N(Ph)C(O)Ph, N(H)Boc, N(Ph)Boc, Ph, CO2Bn, CN), leading to alkyl succinates with preservation of the X group, under Pd(II)-catalyzed oxidative carbonylation conditions, has been developed. Our method shows a completely different inverse chemoselectivity with respect to the "classical" substitutive carbonylation of the allyl compounds, which is known to provide beta,gamma-unsaturated carbonyl derivatives through the formation of a p-allylpalladium intermediate. An accurate study, carried out using allyl acetate as model substrate, allowed to maximize the selectivity in the envisioned 2-CH2X substituted succinates. The best catalyst is generated in situ by mixing Pd(TFA) 2 (TFA= trifluoroacetate) and the N,N'-di(anthracen-9-yl)butane-2,3-diimine ligand. pBenzoquinone was used as oxidant in presence of benzyl alcohol, which acts as a nucleophile and as a solvent, under 4 bar of CO at 20 degrees C. A combined effect of the ligand and the nucleophile, rationalized through DFT calculations, has been observed both in promoting the bis-alkoxycarbonylation process and in preventing p-allylpalladium-mediated side reactions, allowing the attainment of succinate derivatives with moderate to good yields.

A novel and efficient catalytic approach to functionalized furo[3,4-b]indol-1-ones is reported. It is based on a palladium-catalyzed sequential process involving an initial cyclization of 2-(hydroxypropyn-1-yl) anilines to form the indole moiety, followed by insertion of carbon monoxide and a second annulation step to build a lactone ring. In a single transformation, two fused heterocycles and three new bonds (C-N, C-C and C-O) are generated. The present methodology gives direct access to structurally complex molecules starting from readily available reagents.

In this contribution, we report novel palladium-catalyzed carbonylative cascade approaches to highly functionalized polyheterocyclic structures. The Pd-catalyzed carbonylative process involves the regioselective insertion of one to three CO molecules and the sequential ordered formation of up to eight new bonds (one C-O, two C-C, five C-N). The exclusive formation of six-membered heterocycles is elucidated by detailed modeling studies.

A novel methodology to easily access imidazolidin-2-ones from propargylamines, primary amine and CO 2 with TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene) or MTBD (7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene) as catalysts under solvent-free conditions is here reported. Bicyclic guanidines, able to catalyze the formation of oxazolidinones from secondary propargylamines and CO 2 , are now presented for the first time as effective organocatalysts for the chemical fixation of CO 2 into linear and cyclic ureas. Plausible reaction pathways are proposed on the basis of experimental findings.

A new protocol for the alkoxycarbonylation of α-olefins to the corresponding unsaturated esters has been developed. Differently substituted styrenes were selectively converted to cinnamate derivatives, via C H bond functionalization. Various palladium sources, including heterogeneous ones, in combination with CuI exhibited a high catalytic efficiency using oxygen as the most cheap oxidant. Monocarbonylated products were obtained in good yields and high chemoselectivity working with a low CO pressure (2 atm) and an excess of air (35 atm) avoiding in this way explosion risks. Commercial cinnamate derivatives were prepared in good to excellent yields by this very simple one-pot procedure.

Herein, we report a novel catalytic synthesis of substituted 9H-fluoren-9-ols starting from aryl iodides and secondary ortho-bromobenzyl alcohols in the presence of palladium/norbornene as a catalytic system. The present protocol exhibits high functional group tolerance, mild reaction conditions and moderate to good yields. This transformation is based on two sequential pathways: (i) Pd(II)-mediated oxidation of the secondary alcohol to the corresponding ketone and (ii) Pd(0)/norbornene-catalyzed reaction of the in situ generated ortho-bromoacetophenone with the aryl iodide.

The first organo-catalyzed synthesis of imidazolidin-2-ones and imidazol-2-ones via intramolecular hydroamidation of propargylic ureas is reported. The phosphazene base BEMP turned out to be the most active organo-catalyst compared with guanidine and amidine bases. Excellent chemo- and regioselectivities to five-membered cyclic ureas have been achieved under ambient conditions, with a wide substrate scope and exceptionally short reaction times (down to 1 min). A base-mediated isomerization step to an allenamide intermediate is the most feasible reaction pathway to give imidazol-2-ones, as suggested by DFT studies.

A catalytic carbonylative double cyclization method for the synthesis of furo[3,4-b]benzofuran-1(3H)-ones is reported. It is based on the reaction between readily available 2-(3-hydroxy-1-yn-1-yl)phenols, CO, and oxygen carried out in the presence of catalytic amounts of PdI2 (1 mol %) in conjunction with KI (20 mol %) and 2 equiv of diisopropylethylamine at 80 degrees C for 24 h under 30 atm of a 1:4 mixture of CO-air. Interestingly, the process was not selective when carried out in classical organic non-nucleophilic solvents (such as MeCN or DME), leading to a mixture of the benzofurofuranone derivative and the benzofuran ensuing from simple cycloisomerization, whereas it turned out chemoselective toward the formation of the double cyclization compound in BmimBF(4) as the reaction medium. Moreover, the ionic liquid solvent containing the catalyst could be easily recycled several times without appreciable loss of activity.

The first example of the oxidative carbonylation of 2-ethynylbenzoic acid derivatives, leading to alkyl (Z)-2-[3-oxoisobenzofuran-1-(3H)-ylidene]acetates in a regio- and stereoselective manner, is reported. Under the catalytic action of PdI2 (2 mol%) in conjuction with KI (20 mol%), different 2-[(trimethylsilyl)ethynyl]benzoic acids were converted into the corresponding isobenzofuranones in high to excellent yields (70–98%). The proposed reaction mechanism involves syn 5-exo-dig cyclization, carbon monoxide insertion, and nucleophilic displacement by an alcohol. Desilylation occurred under the reaction conditions. The structure of a representative product, that is, methyl (Z)-2-[3-oxoisobenzofuran-1(3H)-ylidene]acetate, was confirmed by XRD analysis. (Figure presented.).

A practical homogeneous and gas‐liquid palladium‐catalyzed Catellani‐type reaction using a continuous‐flow platform is described. The implementation of continuous‐flow technology allowed the acceleration of the transformation and, for the first time, expansion of the chemical space to gaseous olefins (i.e., ethylene, propylene and 3,3,3‐trifluoropropene), thus providing a safe and practical approach to sterically hindered ortho‐disubstituted styrenes and vinyl arenes. The complete control over the stoichiometry of gaseous reagents through flow technology proved essential for directing the selectivity of the Catellani reaction to the desired products.

(S)-4-Isopropyl-5,5-diphenyloxazolidin-2-one has been synthesized for the first time by the enantiospecific oxidative carbonylation of commercially available (S)-2-amino-3-methyl-1,1-diphenylbutan-1-ol. The cyclocarbonylation reaction was carried out at 100 °C in 1,2-dimethoxyethane (DME) as the solvent for 15 h, under 20 atm of a 4:1 mixture of CO–air and in the presence of the catalytic system PdI2/KI (substrate:KI:PdI2 molar ratio = 100:10:1), to give the oxazolidinone derivative in 81% isolated yield.

The combination of a Pd(0) complex with benzoic acid converts propargylic tryptamines to the corresponding tetrahydro-β-carbolines. The method uses unprotected indoles and affords the desired products with ample functional group tolerance. Detailed modeling studies reveal a close synergy between the organic and metal catalysts, which enables sequential alkyne isomerization, indole C–H activation, and eventual C–C reductive elimination to afford the target heterocycles.

Readily synthesized aryl α-diimine derivatives have been used as efficient ligands for the palladium-catalyzed oxidative bis-alkoxycarbonylation reaction of 1,2-disubstituted olefins. The most active catalyst A was formed insitu from bis-(2,6-dimethylphenyl)-2,3-dimethyl-1,4-diazabutadiene and Pd(TFA)2(TFA=trifluoroacetate). This catalytic system was able to selectively convert 1,2-disubstituted olefins into 2,3-disubstituted-succinic diesters with total diastereospecificity, in good yields (up to 97%) with 2mol% of catalyst loading, under mild reaction conditions (4bar of CO at 20°C in presence of p- toluenesulfonic acid as additive and p-benzoquinone as oxidant). The optimized reaction conditions could be successfully applied to 1,2-disubstituted aromatic, aliphatic, cyclic olefins and to unsaturated fatty acid methyl esters, employing methanol or benzyl alcohol as nucleophiles. The use of the bulky, less reactive isopropyl alcohol has allowed to better understand the mechanisms involved in the catalytic process. The geometry of the carbonylated products can be explained as a consequence of a concerted syn addition of the Pd-alkoxycarbonyl moiety to the olefin C=C bond. Catalyst A was isolated, characterized and analyzed by single crystal X-ray diffraction analysis.

Dihydrodibenzo[b,f]azepines and dibenzo[b,f]azepines can be efficiently synthesized from aryl bromides, o-bromoanilines and norbornene or norbornadiene by means of palladium catalysis. This protocol gives access to dibenzo[b,f]azepine core containing a variety of electron-withdrawing substituents on both aromatic rings and complements the previously reported methodology where electron rich aryl iodides were preferentially used. The presence of KI, even in sub-stoichiometric amount, is crucial for this three-component reaction. The proper addition of iodide anions has a dramatic effect on reaction rate and selectivity. A formal three-step synthesis of the tricyclic antidepressant Clomipramine (Anafranil (R)) is also described.

Developments are reported in the catalytic synthesis of biaryls containing an ortho -carbaldehyde or 6 H -dibenzopyrans in the presence of palladium/norbornene as catalyst. The reaction of o -substituted aryl iodides and o -bromobenzyl alcohols proceeds by unsymmetrical aryl-aryl coupling to form a seven-membered oxapalladacycle intermediate, which may undergo an intramolecular redox process to form carbonyl groups or a C–O coupling to six-membered cyclic ethers. The predominant formation of dibenzopyrans as well as of biaryl structures containing the oxidized CHO group in one ring and the reduced CH 2 OH in the other is described along with some mechanistic insights.

The hydroalkoxycarbonylation of terminal arylacetylenes can be carried out in an easy one-step synthesis through the use of PdI 2 or PdI 2 /KI as catalytic systems under non-oxidative conditions, without other ligands and in the absence of added acids. Going from non-polar to polar reaction media, we have noticed a dramatic change in the chemoselectivity of the reaction with prevailing formation of α-, β-unsaturated esters, in the former case, and a mixture of oxidative (maleic esters derivatives) and reductive (mainly unsaturated lactones) carbonylation products in comparable amount, in the latter case. The origin of this behavior can be explained with the different active species at work changing the reaction media: neutral palladium species in non-polar media and ionic palladium species in polar media.

Organometallic and organo-catalysts are cooperatively at work in the enantioselective synthesis of dibenzopyran derivatives; palladium/norbornene and a cinchona alkaloid base guarantee good yields and satisfactory enantioselectivities in a one-pot reaction.

A variety of isocoumarins have been synthesized directly from 2-halobenzoates and ketones through a palladium-catalyzed α-arylation step followed by an intramolecular cyclization process. The addition of iodide anions to the reaction mixture increased yields and selectivities especially when 2-bromobenzoates were employed. This phosphine-free one-pot synthesis features a high functional group tolerance and gives access to richly decorated isocoumarins. This general methodology was successful in the total synthesis of Xyridin A, an important natural product with antibacterial and antifungal activity.

The title compound, (Z)-4-(carbomethoxymethylene)-2-(4-fluorophenyl)-4H-benzo[d][1,3]oxazine, was synthesized in 68% isolated yield by palladium-catalyzed oxidative cyclization-methoxycarbonylation of 4-fluoro-N-(2-((trimethylsilyl)ethynyl)phenyl)benzamide. This new heterocyclic derivative was fully characterized by IR, 1H-NMR, 13C-NMR spectroscopies, MS spectrometry, and elemental analysis. The Z configuration around the double bond was unequivocally established by 2D NOESY experiments.

1,3-Oxazolindin-2-one derivatives were obtained for the first time through carboxylative cyclization of allylamines in the absence of any metal or base catalyst. An electron-withdrawing substituent on the allylic double bond is crucial for the reaction success. Allylamines react with CO2 in MeCN/MeOH mixture and in scCO2 giving satisfactory results.

A method to obtain aryl nitriles from the corresponding halides by Pd catalysis, in the absence of any cyanide source, is reported. The reaction of an aryl halide, ethyl nitroacetate, and an olefin readily delivers an aromatic nitrile. A variety of aryl iodides/bromides have been converted into the corresponding cyanoarenes in fair to excellent yields. The reaction likely involves the following steps: (a) Pd-catalyzed α-arylation of ethyl nitroacetate; (b) nitrile oxide formation; (c) [3 + 2]-cycloaddition with an olefin to provide an isoxazoline; (d) isoxazoline cleavage to benzonitrile formation.

An efficient reaction protocol for the palladium-catalyzed synthesis of 2,4-diacetoxycyclopentylideneacetates by a reaction of acetic acid with 3,6-heptadienoic esters, has been developed. The process, which occurs in the presence of oxidants, represents the first example of sequential double acetoxylation–cyclization of substituted 1,4-dienes to form cyclopentane rings with oxygen functionalities at 2 and 4 carbon atoms. The use of a water/acetic acid reaction medium has also been shown to give satisfactory results.

o-Biaryl carbaldeydes and ketones are obtained through the one-pot reaction of o-aryl iodides with o-bromobenzyl alcohols under the catalytic action of Pd and norbornene, in the presence of a base. The same reaction can also give dibenzopyrans by Pd and norbornene catalysis with a different termination, leading to C-O ring closure. In both cases the process first leads to a five-membered palladacycle, which controls C-C coupling, then to a seven-membered oxapalladacycle, which gives aldehydes and ketones or dibenzopyrans.

Direct C-H bond activation is an important reaction in synthetic organic chemistry. This methodology has the potential to simplify reactions by avoiding the use of prefunctionalized reagents. However, selectivity, especially site selectivity, remains challenging. Sequential reactions, in which different molecules or groups are combined in an ordered sequence, represent a powerful tool for the construction of complex molecules in a single operation. We have discovered and developed a synthetic methodology that combines selective C-H bond activation with sequential reactions. This procedure, which is now known as the "Catellani reaction", enables the selective functionalization of both the ortho and ipso positions of aryl halides. The desired molecules are obtained with high selectivity from a pool of simple precursors. These molecules are assembled under the control of a palladacycle, which is formed through the joint action of a metal (Pd) and an olefin such as norbornene. These two species act cooperatively with an aryl halide to construct the palladacycle, which is formed through ortho-C-H activation of the original aryl halide. The resulting complex acts as a scaffold to direct the reaction (via Pd(IV)) of other species, such as alkyl or aryl halides and amination or acylation agents, toward the sp(2) C-Pd bond. At the end of this process, because of steric hindrance, the scaffold is dismantled by norbornene extrusion. Pd(0) is cleaved from the organic product through C-C, C-H, C-N, C-O, or C-B coupling, in agreement with the well-known reactivity of aryl-Pd complexes. The cycle involves Pd(0), Pd(II), and Pd(IV) species. In particular, our discovery relates to alkylation and arylation reactions. Recently, remarkable progress has been made in the following areas: (a) the installation of an amino or an acyl group at the ortho position of aryl halides, (b) the formation of a C-B bond at the ipso position, (c) the achievement of meta-C-H bond activation of aryl rings bearing a chelating directing group by Pd(II)/Pd(IV)/norbornene catalysis, and (d) the activation of N-H and C-H bonds in sequence for indole 2-alkylation. In this Account, we explain the main features of this methodology, describe its synthetic potential, and illustrate some remarkable progress that has been made, emphasizing the most recent developments and applications in total synthesis.

An efficient palladium-catalyzed synthesis of symmetrically disubstituted ureas via oxidative carbonylation of primary amines is described. The reactions are carried out in the presence of a large excess of carbon dioxide as reaction medium or under solvent-free conditions. The adopted catalyst such as potassium tetraiodopalladate, stable and easy to prepare, allows the use of air as a cheap oxidizing agent. The reactions yield urea and water as the only by-product and proceed with high efficiency with aliphatic and aromatic amines as well. While with primary aliphatic amines, no significant improvement on reactivity is observed when carbon dioxide is used as a solvent, in comparison with the conventional ones, a remarkable high efficiency is obtained with aromatic amines, which shows a dramatic increase in the performance of the catalyst, in terms of turnover number (TON), the highest known so far for this kind of process. Reactions take place in two-phase systems consisting of a homogeneous liquid phase formed by the CO2 expanded amine solution containing the catalyst and a supercritical phase of CO2, CO, O2, and N2.

The reactions of propargyl alcohols with carbon dioxide in supercritical carbon dioxide or in acetonitrile with gaseous carbon dioxide in the presence of organic bases as catalysts have been examined. Bicyclic guanidines are effective catalysts for the formation of α-methylene cyclic carbonates under mild reaction conditions. Oxoalkyl carbonates, oxoalkyl carbamates or α-methyleneoxazolidinones are obtained in high yields and good selectivities in one-step starting from propargyl alcohols and an external nucleophile (alcohols or amines) using bicyclic guanidines as catalysts in supercritical carbon dioxide. Propargylic diols under the same reaction conditions underwent a rearrangement process instead of carbon dioxide insertion whereas in the presence of an external nucleophile the formation of oxocarbonates, oxocarbamates or cyclic carbamates was achieved in satisfactory yields.

A catalytic synthesis of selectively substituted phenanthridines is achieved through a reaction sequence involving palladium/norbornene-catalyzed unsymmetrical aryl-aryl and Heck couplings followed by aza-Michael and retro-Mannich reactions. In spite of the many steps involved the method is very simple and allows the formation of selectively substituted phenanthridines under mild conditions in a straightforward one-pot reaction starting from readily available aryl iodides and bromides.

In the process of developing our aryl coupling methodology according to which aryl iodides are caused to react with aryl bromides under the catalytic action of a dual palladium/norbornene catalyst, we have worked out new protocols to cause appropriate functional groups in the aryl halides to form heterocyclic rings condensed with the first-formed biaryl intermediate. Carbazoles, dibenzopyrans, phenanthridines and azaphenanthrenes have been obtained with good yields in one-pot reactions under mild conditions.

The title compound—cis,exo-1,2,3,4,4a,13b-hexahydro-1,4-methano-5-isopropoxy-9H-tribenzo[b,f]azepine—was synthesized in 83% isolated yield by a palladium-catalyzed one-pot strategy from 1-iodo-2-isopropoxybenzene and ortho-bromoaniline. The azepine derivative was fully characterized (FT-IR, MS, 1H and 13C-NMR, elemental analysis) and all proton and carbon signals have been completely assigned by 2D NMR experiments.

The present review refers to catalytic methods to arylate arene or heteroarene compounds. The resulting compounds are ubiquitous in biology and in pharmaceuticals or fine chemicals production. Until a few decades ago they were prepared according to laborious procedures often involving a series of steps all requiring product isolation. Catalytic methods are much simpler and convenient and often consist of one-pot procedures leading to highly selective reactions. The reaction types described here encompass intermolecular as well as intramolecular reactions. Assistance by chelating groups, heteroatoms and metallacycles are considered for metal-catalyzed reactions not involving the use of oxygen or stoichiometric oxidants.

Differently substituted alkynyloxiranes were efficiently converted into functionalized 1,3-dihydroisobenzofurans and tetrahydrofuran derivatives in fair to good yields by a new cascade reaction, consisting of a sequential nucleophilic ring opening–heterocyclization–oxidative carbonylation process. Reactions were carried out at 80–100 °C and under a 3:1 mixture of carbon monoxide and air (total pressure=32–42 atm at 25 °C) in methanol or acetonitrile/methanol mixtures in the presence of catalytic amounts of palladium diiodide in conjunction with an excess of potassium iodide. The nucleophilic species beginning the cascade process by regioselective attack to the less hindered carbon of the oxirane ring can be methanol itself or iodide anions.

The present paper offers a synthetically simple one-pot procedure for the catalytic preparation of the biologically interesting class of carbazoles. The new procedure is based on the combined catalysis of palladium and norbornene starting from o-substituted iodoarenes and N-sulfonylated or N-acetylated o-bromoanilines. A well-known member of this class, carbazomycin A, has been successfully prepared.

Catalytic methods are important tools for the synthesis of C-C bonds under mild and ambient conditions. Palladium chemistry predominates in this area because it offers the opportunity to form several different types of bonds in one pot. Palladium can also tolerate a variety of functional groups. Among the many investigations of catalytic aryl-aryl couplings, the most successful technique has been the Suzuki reaction, which uses an arylboronic acid to attack an aryl-Pd bond. This Account reports our methodology, based on the cooperative action of Pd and norbornene, that achieves selective aryl-aryl coupling through C-halide and C-H activation. We are primarily interested in Pd-catalyzed sequential reactions. These reactions combine palladium as an inorganic catalyst and a strained olefin such as norbornene as an organic catalyst and can lead to biphenyl derivatives. While the palladium facilitates C-C bond formation through C-halide and C-H activation, the norbornene contributes to the construction of a palladacycle, an intermediate structure that controls and directs the subsequent reaction steps selectively. To achieve regioselective arylation at the carbon ortho to the original C-halide bond, palladacycles require an additional ortho substituent (R(1)). The palladacycle opens, giving rise to a biphenylylnorbornylpalladium complex. Because of the steric hindrance exerted by the two ortho groups, norbornene deinsertion readily occurs to form a biphenylylpalladium complex. Thus, norbornene acts as a removable scaffold. We used this biphenylylpalladium species to form C-C (with olefins, alkynes, or arylboronic acids) or C-H bonds (by hydrogenolysis). Using nonidentical aryl or heteroaryl halides, we also formed a biaryl-bonded Pd species able to undergo the final termination reaction (C-C, C-N, or C-O bond formation) either inter- or intramolecularly. We used this method to synthesize a variety of aromatic and heteroaromatic compounds. We also obtained the key metallacycle able to selectively direct the reactions by replacing norbornene with an aryl-bonded aminocarbonyl group. This method provided a diverse series of condensed heterocycles.

Organometallic and organo-catalysts are cooperatively at work in the enantioselective synthesis of dibenzopyran derivatives; palladium/norbornene and a cinchona alkaloid base guarantee good yields and satisfactory enantioselectivities in a one-pot reaction.

The direct syntheses of ureas, oxamides, 2-oxazolidinones, and benzoxazolones by the oxidative carbonylation of amines, β-amino alcohols, and 2-aminophenols allows us to obtain high value added molecules, which have a large number of important applications in several fields, from very simple building blocks. We have found that it is possible to perform these transformations using the PdI2 /KI catalytic system in an ionic liquid, such as 1-butyl-3-methylimidazolium tetrafluoroborate, as the solvent, the solvent/catalyst system can be recycled several times with only a slight loss of activity, and the product can be recovered easily by crystallization.

Eleven novel ligands having picolinamide or thiopicolinamide binding groups at the upper or lower rim of calix[4]-, calix[6]- and calix[8]arenes have been synthesised. The conformational properties of some of these ligands were studied in solution by means of NMR spectroscopy and in the solid state by X-ray diffraction. Their ability to extract AmIII or EuIII from water to NPHE (o-nitrophenyl hexyl ether) was tested at different concentrations of LiNO3, HNO3 and of a lipophilic dicarbollide anion (BrCosan). The data show a high cooperation between binding sites of the calixarene ligands in comparison to data obtained with the model ligand N-butyl picolinamide (19). Some of these ligands show very high distribution coefficients for Am3+ (DAm > 300) and good Am/Eu selectivity at pH ≥ 3, which open up interesting perspectives for their application in the treatment of low acidity radioactive waste. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Ab initio calculations in the gas-phase indicate that the substitution of an ethylene with a propylene moiety in the polyether bridge of 1,3-di- iso -propoxycalix[4]arene-crowns-6 could result in an enhanced Cs + /K + selectivity which is of particular interest in nuclear waste treatment. We therefore synthesised two novel calix[4]arene-crown-6 compounds ( 1 and 2 ) having a propylene moiety in their structure and for this named calix[4]arene-propylene-crown-6. The structures of compounds 1 and 2 were elucidated by NMR in solution and for 1 also by X-ray diffraction studies in the solid state. Association constants ( K a ) in CHCl 3 of the two novel calix-crowns were measured and pointed out a plateau selectivity towards alkali metal ions which was not predicted by molecular modelling calculations. These results indicate the important role played by the solvent molecules and counter-anions in binding for this class of ionophores.

A direct synthesis of 1-(alkoxycarbonyl)methylene-1,3-dihydroisobenzofurans 2 and 5 and 4-(alkoxycarbonyl)benzo[c]pyrans 3 and 6 by oxidative Pd-catalysed cyclization/alkoxycarbonylation of 2-alkynylbenzyl alcohols 1, and of 2-alkynylbenzaldehydes or 2-alkynylphenyl ketones 4 is reported. Reactions were carried out in ROH or CH3CN/ROH (R = Me, iPr) as the solvent at 70−105 °C in the presence of catalytic amounts of PdI2 in conjunction with KI under a 4:1 or 3:1 CO/air mixture (2.0 or 3.2 MPa total pressure at 25 °C). The reaction occurs through intramolecular attack by the nucleophilic oxygen atom (either already present in the starting material, as in 1, or generated in situ by ROH attack on carbonyl group, as in 4) on the triple bond coordinated to PdII, followed by alkoxycarbonylation. The presence of substituents at the alkyne terminal position and at the carbon atom α to the hydroxy group play a key role in the selectivity of the process towards the formation of a five- or six-membered ring. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The novel method allows the carbonylative cyclization of allylamines in the absence of any metal or base catalyst.

Depending on the reaction conditions, mono- and diacetoxylated cyclopentanone derivatives can be prepared.

The reactions of propargyl alcohols with carbon dioxide in supercritical carbon dioxide or in acetonitrile with gaseous carbon dioxide in the presence of organic bases as catalysts have been examined. Bicyclic guanidines are effective catalysts for the formation of α-methylene cyclic carbonates under mild reaction conditions. Oxoalkyl carbonates, oxoalkyl carbamates or α-methyleneoxazolidinones are obtained in high yields and good selectivities in one-step starting from propargyl alcohols and an external nucleophile (alcohols or amines) using bicyclic guanidines as catalysts in supercritical carbon dioxide. Propargylic diols under the same reaction conditions underwent a rearrangement process instead of carbon dioxide insertion whereas in the presence of an external nucleophile the formation of oxocarbonates, oxocarbamates or cyclic carbamates was achieved in satisfactory yields.

Selectively substituted biaryls containing a ketone unit are obtained under mild conditions in satisfactory yields by a simple reaction of ortho-substituted aryl iodides and ketones in the presence of palladium and norbornene as catalysts.